Anyone who has ever had a bedbug infestation knows full well what a nuisance the pests can be. Unlike ticks and mosquitoes, however, bedbugs, which feed on human blood, are not known to spread disease and are generally not viewed as a major public health threat.

But a peer-reviewed study published online Wednesday in a journal of the U.S. Centers for Disease Control and Prevention suggests the pests could play a role in transmitting disease. In a tiny sample of bedbugs, collected from a small number of residents living in crowded conditions in a poor neighborhood in Canada, researchers found the drug-resistant bacterium known as MRSA.

The researchers at a Vancouver, B.C., hospital tested three patients from the neighborhood who were infested with bedbugs. Researchers collected five bedbugs and determined that the insects carried two types of drug-resistant bacteria. Three bedbugs from one patient contained methicillin-resistant Staphylococcus aureus (MRSA), and the two from the other patients each contained vancomycin-resistant Enterococcus faecium (VRE).

MRSA has increasingly turned up in hospitals and in outbreaks outside of health-care settings, such as among athletes, prison inmates and children. MRSA, which is spread by casual contact, can cause serious health problems, including disfiguring “necrotizing” abscesses that eat tissue and life-threatening infections if the microbe gets into vital organs.

“Even though this is a small study, it suggests that bedbugs may be playing a role in the transmission of MRSA in inner-city populations where bedbug infestations are a problem,” said Marc Romney, one of the study’s authors. Romney is medical director of infection prevention and control at St. Paul’s Hospital.

Other experts said the new information was interesting but inconclusive.

“It emphasizes the need for some further studies to determine the potential bedbugs have for transmitting these agents,” said Robert Wirtz, chief of entomology at the CDC’s Center for Global Health. “While the work was well done and it shows an association, it doesn’t establish that bedbugs are capable of transmitting the bacteria.”

The study leaves many key questions unanswered. It did not determine whether the bacteria were transmitted from bugs to patients or the other way around. Nor did it determine whether the bacteria were on the outside of each bug or living and growing inside it, which would be more significant, researchers said.

But even if the bugs were carrying the bacteria on their exteriors, the finding is still significant, Romney said. Bedbugs could spread the germ from person to person, especially in crowded places, such as the homeless shelters where many patients were living in downtown Vancouver. The bacteria typically survive for hours, and possibly days, under the right conditions, he said.

Residents in that Vancouver community tend to be more susceptible to infection because their immune systems are compromised by chronic illness, drug use, crowding and poor nutrition.

Vancouver, like New York, Washington and other cities, has had a disturbing increase in bedbugs in recent years. Experts suspect the resurgence is related to greater domestic and international travel, to the bugs’ resistance to available pesticides, and to lack of knowledge about pests that were virtually eradicated in the 1940s and ’50s by widespread used of DDT. The insecticide was banned in the 1970s.

Bedbugs can live for months without a meal, hidden deep in mattress seams, baseboard cracks and clutter near beds. They travel easily, hitchhiking from person to person, city to city. They have turned up in college dorms, government buildings, Google’s offices and even luxury hotels such as the Waldorf-Astoria, which has been sued by guests who say they were bitten at the New York landmark.

Researchers in Canada wanted to know whether bedbugs may spread the bacteria in poor, overcrowded communities, such as the downtown area where the patients lived.

The CDC’s Wirtz said the next step should be to determine whether a colony of bedbugs fed with blood infected with MRSA or VRE could transmit the bacterium to a clean, sterile system, he said.

Bedbug research has focused more on insecticide resistance and less on public-health effects, scientists said, because they are not known to spread disease.

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